Osservatorio Astronomico di Roma

colloquium - Mauro Centrone
2019-05-07 11:45 - 12:45 (Europe/Rome)

Lithium Web in astrophysics: insights and problems
2019-04-16 11:45 - 12:45 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia
Lithium (Li) is widely used as a test of the cosmological model, a probe of stellar structure, and an age indicator of young stellar clusters. It is the very element that presents deep insights, yet many problems to astrophysics.
I will discuss problems and puzzles that Li introduces in astrophysics, including cosmological Li problem (and a stellar solution to it), Li-rich giants problem (Galactic and extraGalactic), Li problem in the Sun, the Galactic Li evolution (in the thin and thick discs), and the interstellar Li content.

A MUSE view of the multiple populations' chemistry in Galactic Globular Clusters
2019-04-09 11:45 - 12:45 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia
Stars in Galactic globular clusters are known to exhibit abundance variations in specific elements such as He, C, N, O, Na, and Al. These variations can be observed via spectroscopy but also photometrically by using CMD constructed with various filter combinations. Although these multiple populations have been, and still are, the subject of many investigations, the origin of their elemental abundance variations remain rather mysterious.
I will present some of our recent results on that topic based on the spectroscopic survey of 26 globular clusters that is currently carried out as part of the MUSE GTO time. With the MUSE survey covering the central regions of the clusters for which HST photometry is available, we can use these photometric catalogs to separate the RGB stars into two or more populations based on their position in the pseudo-two-color diagrams. Although the MUSE spectra are of relatively low-resolution (R ~ 2500), by combining the spectra of the stars within a distinct populations, we are able to study their abundance variations and relate them directly with the populations distinguished on the pseudo-two-color diagrams.

colloquium - Elena Valenti
2019-03-26 11:45 - 12:45 | Aula Gratton

How quasars affect the formation of the bright cluster galaxy and the circum-galactic medium
2019-03-19 11:45 - 12:45 | Aula Gratton
AGN activity is considered a fundamental phase of the evolution of the massive galaxies. The accretion onto a SMBH generates a great amount of energy in the form of radiation, outflows and radio jets that affects both the ISM and CGM. In this talk, I present the results of two multi-wavelength studies aimed at exploring how nuclear activity affect the formation of the bright cluster galaxy and the circum-galactic medium at high redshift. Firstly, I will report on the multi-band analysis of the galaxy population in the very dense core (~70 x 70 kpc^2) of one of the most massive galaxy clusters at z ~ 1.6. We are able to shed light on the early, poorly-explored phase of the assembly of the Brightness Cluster Galaxy (BCG) in a region with high AGN and merger activity.
I will also report on the properties of both an extended (150 kpc) and luminous (10^44 erg/s) Lya nebula and the associated CIV extended (70 kpc) emission around a hyper-luminous quasar at z~3.6. Our analysis of kinematics of the Lya nebula suggests the presence of a spatially coherent blueshifted (~1000 km/s) component on several tens of kpc scales which we interpret as one of the first indications of an AGN-driven outflow propagating on circum-galactic scales.

Neutrinos from a blazar jet and the birth of non-stellar neutrino astronomy
2019-03-14 11:45 - 12:45 | OAR Monte Porzio Catone – aula Gratton, Via Frascati 33, Roma, RM, 00136, Italia
IceCube has recently reported the discovery of high-energy neutrinos of astrophysical origin,
opening up the PeV (10^15 eV) sky. These observations are challenging to interpret on the
astronomical side and have triggered a fruitful collaboration across particle and astro-physics.
I will discuss the very recent association between high-energy IceCube neutrinos and the
blazar TXS 0506+056, reporting on how this result fits with the work done by our group over
the past five years. I will then present the “big picture”, explain why this this association is
very important for astronomy, and discuss some very recent results on the nature of TXS 0506+056.
The talk is self-contained, requires no previous knowledge of neutrinos or blazars, and has been
prepared for a very broad audience.

colloquium - Roberto Speziali
2019-03-12 11:45 - 12:45 | Aula Gratton

LBT - Italia
2019-03-12 11:45 - 12:45 | Aula Gratton
LBT – ITALIA è un’organizzazione formata da un team di ricercatori dell’INAF che ha come obiettivo la gestione delle osservazioni al LARGE BINOCULAR TELESCOPE. A distanza di sette anni dall’inizio delle operazioni, si fornirà una panoramica della strumentazione e si descriverà l’attività del gruppo illustrando i risultati ottenuti.
Al termine del seminario, ampio spazio verrà dato alla discussione al fine di ricevere feddback da parte degli utenti
che hanno già usufruito dei servizi di LBT-ITALIA e rispondere alle domande in vista della imminente apertura della call 2019-2020.

Flipping a fair coin to decipher the large-scale environment of radio galaxies
2019-03-05 11:45 - 12:45 | Aula Gratton
The role played by the large-scale environment in the nuclear activity of radio galaxies is still not completely understood. Accretion mode, jet power, and galaxy evolution are connected with their large-scale environment on scales from tens to hundreds of kiloparsecs. I am presenting a detailed statistical analysis of the large-scale environment for two samples of radio galaxies in the local Universe (i.e., up to redshift 0.15).
I will discuss on a direct search of galaxy-rich environments around radio galaxies by using them as beacons. To carry out this study a new method, that does not appear to suffer cosmological biases and artifacts, as other algorithms, was developed. I conclude that, despite their radio morphological classification (FRI versus FRII) and/or their optical classification (high- or low-excitation radio galaxy, i.e., HERG or LERG), radio galaxies in the local universe tend to live in galaxy-rich large-scale environments that have similar characteristics and richness. I will then show that properties of large-scale environments of both FRIs and FRIIs do not depend by the property of central radio galaxy. Finally, I will provide an estimate of the X-ray parameters that can be derived from optical observations to plan future follow up campaigns.

colloquium - Francesco Massaro
2019-03-05 11:45 - 12:45 | Aula Gratton

When the going get tough... or: observation and laboratory work for life searching in other worlds
2019-02-26 11:45 - 12:45 | Aula Gratton
“…if we never search, the chance of success is zero”. This was the conclusion in the seminal paper of G. Cocconi and P. Morrison in 1959 about the search for life. Since then, a lot of progress in technology and a lot of exciting results in astrophysics have been reached. Today, we know that, out of there, there are more than 4000 new worlds showing a large diversity in their size and orbital characteristics. In the midst of all these strange new worlds, a very promising type of them, the super Earths, seems to be ubiquitous in the Galaxy. Moreover, in fashion there are super Earths orbiting M stars. But, such an odd couple could host life? And if it can, how to find it?

colloquium - Guido De Marchi
2019-02-19 11:45 - 12:45 | Aula Gratton

Star formation in the Local Group
2019-02-19 11:45 - 12:45 | Aula Gratton
Using Hubble Space Telescope (HST) observations, we have identified and
characterised almost 50,000 pre-main sequence (PMS) stars in several
star-forming regions in the Milky Way and Magellanic Clouds. These objects
are still undergoing active mass accretion, as revealed by excess emission
in the Halpha band. Detailed knowledge of the extinction law in these
fields, which we derive directly from the observations, allows us to
accurately obtain stellar physical parameters (temperature, luminosity,
age, mass, and mass accretion rate). This is presently the largest and
most homogeneous sample of PMS objects, on which we are conducting the
first comprehensive and systematic study of the PMS phase, spanning a wide
range of masses (0.5-4 Msun), metallicities (0.1-1 Zsun) and ages (0.5-30
Myr).
I will discuss how star formation has proceeded in these regions over
multiple recent bursts and how the accretion process depends on the
physical properties of the individual stars and of the environment. We
have discovered an important dependence of the mass accretion rate on
metallicity: mass accretion rates for stars of the same mass and age are
systematically higher in the Magellanic Clouds than in the Milky Way and
are expected to have been equally high at redshift z~2, when star
formation was at its peak in the Universe. I will also show a surprising
anti-correlation between the variability and intensity of the Halpha
excess: this suggests a discrete and clumpy nature for the accretion
process and reveals that the characteristic mass of the infalling parcels
of gas is comparable to that of the moons of giant planets in the solar
system.
To close, I will illustrate how we plan to thoroughly verify these results
spectroscopically and to extend them to lower mass objects and to more
extinguished environments through already planned guaranteed-time
observations with the James Webb Space Telescope. Our measurements will
provide, for the first time, quantitative information on the nature,
excitation, and kinematics of the infalling gas in these dense environments.

colloquium - Giuseppe Tanzella-Nitti
2019-02-14 11:45 - 12:45 | Aula Gratton

Colloquium - Marianna Torelli
2019-02-12 11:45 - 12:45 | Aula Gratton

Stellar Populations in Local and high redshift Universe
2019-02-12 11:45 - 12:45 | Aula Gratton
Synthetic stellar libraries are quite popular to constrain the stellar pop-
ulations (age and metallicity distribution) of unresolved systems like high redshift galaxies.
However, they are typically based on theoretical Spectral Energy Distributions (SEDs).
It is important to build up empirical synthetic stellar li-
braries, calibrated on local systems and
covering a broad range in ages (globular clusters, old open clusters),
chemical compositions (iron, alpha, CNO) and dynamical properties (nearby
dwarf galaxies), able to improve our SED fitting codes to deeply investigate
high redshift galaxies.
To do that, I am taking advantages of a sample of 65 Galactic globular clus-
ters (GGCs) for which we have accurate and homogeneous optical photometry
based on space (ACS at HST, innermost regions) and ground-based
(up to the tadial radius).
In particular, I will present the results on the study of the Horizontal Branch
(HB) morphology for 64 GGCs in our sample.
I will introduce a very new photometric morphology index based
on the cumulative density function of the stars along the HB,
useful to investigate the well known “second
parameter problem” affecting age estimations and so, stellar libraries.
I will also discuss the results of the analysis on galaxy
evolution through the Galaxy Stellar Mass Function (GSMF) up to redf-
shift 4, obtained combining all the five CANDELS fields (GOODS-South,
GOODS-North, EGS, COSMOS, UDS), the Frontier Fields Parallels (Abell 2744,
MACSJ0416, MACSJ0717, MACSJ1149) and the Ultravista/COSMOS
field. Stellar masses have been estimated fitting the photometry to syn-
thetic models: these surveys are characterized by multi-wavelength (deep
optical/near-infrared/mid-infrared) coverage (CANDELS), very high limiting magnitudes
(Frontier Fields) and large areas (UltraVista), allowing to explore the GSMF
from low masses to the high-mass end.

colloqium - Eva Villaver
2019-02-05 11:45 - 12:45 | Aula Gratton

From AGB stars to Planetary Nebulae: what the ISM, stellar rotation, and companions can do
2019-02-05 11:45 - 12:45 | Aula Gratton
Asymptotic giant branch (AGB) stars lose their envelopes by means of heavy mass-loss rates. Besides the mass-loss process itself there are other mechanisms that influence the evolution of the star and of what we see as Planetary Nebulae. Among them are the interaction of the ejecta with the interstellar medium (ISM), the inclusion of stellar rotation and/or the presence of a companion. I will present our simulation of the interaction process between AGB stars and the ISM. I will show what we can expect for the planetary nebula formation when we include rotation in stellar evolution models and finally I will describe how these stars are influenced by the presence of external companions

Ultraviolet imager with wide-field & deep for astronomical observation and study
2019-01-30 11:45 - 12:45 | Aula Gratton
Base on the ultraviolet radiation characteristics of cosmic celestial models and different morphological materials, the astronomical ultraviolet band observation has important scientific significance and research value for the study of astronomical scientific problems such as searching for the cosmic missing baryons, studying the transport process of stellar and galaxies in the cosmic environment. China is currently developing the space station optical facility with an observation band covering near ultraviolet to infrared range. The wide-field deep ultraviolet imager (WDUI) is proposed on the optical facility of the China space station (CSS), which can overcome the influence of the Earth’s atmosphere and obtain the remarkable astronomical observation efficiency in the ultraviolet band. It promotes the development level of the astronomical ultraviolet band observation instrument and promotes the observation of the ultraviolet astronomical section of the space astronomical science. Output of scientific achievements has a positive effect. This talk reviews the background of the payload proposal, the astronomical observation capability of the CSS optical facility, the scientific goals of the payload, the preliminary system design and technical characteristics of the payload, and possible other band observations.

colloquium - Antonio Stamerra
2019-01-29 11:45 - 12:45 | Aula Gratton

Multimessenger astrophysics with active galactic nuclei: observational clues of gamma-neutrino connection in blazars
2019-01-29 11:45 - 12:45 | Aula Gratton
The clear detection of an isotropic flux of very high energy neutrinos by the IceCube experiment has opened the quest for the identification of their possibile electro-magnetic (EM) counterparts. Active Galactic Nuclei (AGNs) of the blazar category are considered as the main cosmic neutrino source candidates, although contribution from other types of active galaxies and Galactic sources is expected. Observation of transient EM emission, spatially and temporally compatible with the IceCube neutrinos, is crucial to identify their possible counterpart. Since April 2016, the IceCube Collaboration alerts the astronomical community whenever a high-energy single neutrino-induced event – HESE – is detected. Thanks to the IceCube real time system and the fast space- and ground-based observations which followed the alert, a neutrino event recorded on Sept. 22nd, 2017, has been significantly associated for the first time to a quasi-simultaneous gamma-ray flare observed by Fermi-LAT, AGILE and the MAGIC experiment from the AGN blazar TXS 0506+056. In this talk, we will review this multi-messenger result, mainly focussing on the MAGIC detection, and we will present some new results about possible transient gamma-ray sources observed by AGILE, coincident in time and space with public IceCube HESE neutrino events.

colloquium - Viola Allevato
2019-01-22 11:45 - 12:45 | Aula Gratton

Clustering dependence of X-ray AGN on host galaxy properties
2019-01-22 11:45 - 12:45 | Aula Gratton
The presence of a super massive BH in almost all galaxies in the Universe is an accepted paradigm in astronomy. How these BHs form and how they co-evolve with the host galaxy is one of the most intriguing unanswered problems in modern Cosmology and of extreme relevance to understand the issue of galaxy formation. Clustering measurements can powerfully test theoretical model predictions of BH triggering scenarios and put constraints on the typical environment where AGN live in, through the connection with their host dark matter halos. In this presentation I will talk about the clustering properties of X-ray AGN from both an observational and theoretical point of view, using the new catalog of AGN detected by Chandra in COSMOS and semi-empirical models. The Chandra COSMOS-Legacy catalog is one of the largest available sample of X-ray AGN for clustering studies, allowing clustering measurements as a function of obscuration, luminosity and AGN host galaxy properties.

colloqium - Cristina Ramos Almeida
2019-01-15 11:45 - 12:45 | Aula Gratton

An infrared and sub-mm view of AGN obscuration and feedback
2019-01-15 11:45 - 12:45 | Aula Gratton
In the past 10-15 years our view of AGN has significantly evolved thanks to the combination of new observations and models. X-ray, infrared and sub-mm data have been crucial to peer into the inner region of AGN and study the properties of the tori, circum-nuclear disks and nuclear outflows. In this talk I will summarize our current view of nuclear obscuration in AGN, focusing on the variations of the torus properties with gas phase. I will also present preliminary results of a new project aimed to characterize nuclear outflows in three gas phases (ionized, coronal and molecular) in a sample of nearby type-2 quasars and study their impact in the stellar populations, on-going star formation and molecular gas reservoirs of the galaxies.

colloquium - Gioia Rau
2018-12-18 11:45 - 12:45 | Aula Gratton

How to tackle a giant Star: multi-wavelength studies of cool, evolved stars, using HST and VLTI
2018-12-18 11:45 - 12:45 | Aula Gratton
The chemical enrichment of the Universe is considerably affected by the contributions of Giant stars. Giant and supergiant stars are surrounded by a hot layer called the chromosphere, which could likely powers Magneto-Hydrodynamic Alfven waves that could initiate their mass loss. Toward the end of their life, on the Asymptotic Giant Branch (AGB), stars produce heavy chemical elements, molecules, and dust, which, through the mass loss provided via their stellar winds, are placed into the interstellar medium.
This talk will explore ongoing work modeling high-resolution spectroscopic observations with Hubble Space Telescope instruments (Rau et al. 2018), to reveal the role of the chromosphere in driving K-M giant and supergiant winds. Our results include estimates of wind and chromospheric parameters, mass-loss rates, and fundamental stellar parameters.
In addition, ground-based interferometric measurements with high-angular resolution instruments from VLTI, such as MIDI (Rau et al. 2015, Rau et al. 2017), GRAVITY (Wittkowski, Rau et al. 2018), help to test geometrical and dynamical models describing the behavior of the outer AGB atmospheres at various spatial scales. In this way we are able to unravel the role of molecules and dust in their extended atmospheres.
Future plans include the use of high-angular resolution instruments such as VEGA at CHARA, and MATISSE at VLTI, to better understand the behavior of cool stars outer atmospheres at various spatial scales.

colloquium - Marco Padovani
2018-12-11 11:45 - 12:45 | Aula Gratton

The role of cosmic rays on physical and chemical processes of the interstellar medium
2018-12-11 11:45 - 12:45 | Aula Gratton
The study of the interaction of cosmic rays with the interstellar matter is a multi-disciplinary investigation that involves the analysis of several physical and chemical processes: ionisation of atomic and molecular hydrogen, energy loss by elastic and inelastic collisions, energy deposition by primary and secondary electrons, gamma-ray production by pion decay, the production of light elements by spallation reactions, and much more. Cosmic-ray ionisation activates the rich chemistry of dense molecular clouds and determines the degree of coupling of the gas with the local magnetic field, which in turn controls the collapse timescale and the star-formation efficiency of a molecular cloud. In recent years a wealth of observations from the ground and from space has provided information and constraints that still need to be incorporated in a consistent global theoretical framework. My goal is to use the results of chemical models and state-of-the-art numerical simulations supplemented by dedicated observations to provide a unifying interpretation of the data with a model of cosmic-ray propagation specifically developed to make predictions that can be tested against the observations. Finally, I will talk about my most recent study: a mechanism able to accelerate local thermal particles in protostars that can be used to explain the high ionisation rate as well as the synchrotron emission observed towards protostellar sources.

Paolo Dal Pozzo Toscanelli, Cosimo de’ Medici and the Sky of the Magi: a new reading of the Florentine Celestial Hemispheres in the Sagrestia Vecchia at San Lorenzo and in the Pazzi Chapel at Santa Croce.
2018-12-06 11:45 - 12:45 | Aula Gratton
After 30 years since the historical pubblication of the analysis
conducted by Forti, Lapi Ballerini, Monsignori Fossi and Ranfagni (1987), I
offer a careful re-examination of the two famous florentine starry vaults of
the early Renaissance, taking into account the recent restoration of the
hemisphere of the Pazzi Chapel and the almost coeval maps drawn by Paolo
Dal Pozzo Toscanelli for his studies of comets in 1456 (Halley) and 1457.
The authorship by the Tuscan cosmographer is confirmed in the Sagrestia
Vecchia on the basis of a comparison between a sample of stars from the
dome, Toscanelli’s maps and Ptolemy’s Catalogue. The Pazzi Chapel instead,
reveals on close inspection to be a clumsy, derivative later work.
While the double date proposed in 1987, the enigmatic 4/5 july 1442, still
remains astronomically the most probable, I will show that the exactness of
the planetary positions have been overestimated, unfairly provoking a lack of
attention for other candidate dates, more astrologically meaningful if not
depicted with satisfying correctness. Relying indeed on the astrological
techniques and interests of the time, I propose to assess the 1442 and the
1439 most probable candidate horoscopes following the very appropriate line
of reasoning introduced by Dieter Blume (2000), i.e. considering the
congruence of the sky charts with principles and rules of astral divination as
well as with the political situation in Florence and with the cultural needs of
the clients.
Finally, I single out as most probable the second date (even exhibiting a
marginal evidence for it on the basis of Lorenzo de’ Medici’s calendarial
concerns), and I offer a new hypothetical explanation for this preference,
linking medicean interest in the magian narrative and the Star of Bethlehem,
astrological speculation and political propaganda.
